Liquid crystal display (LCD) has the advantages of low radiation and compact size; thus, the LCD is now being widely used and becoming a mainstream display.
Because the liquid crystals do not radiate light, the liquid crystal display needs to utilize a backlight module to serve as a light source. Because light of the light source penetrates the respective layers of the LCD, such as polarizers, color filters, etc., in actuality, the brightness that is really shown is only about ten percent of the original light source brightness. To overcome the problem of inadequate displayed brightness, if the backlight brightness is raised, the brightness of the display panel can be accordingly raised. However, the power consumption of the backlight module is also increased. Therefore, a conventional technique has been proposed to increase the aperture ratio of the pixels on the display panel so as to improve the brightness of the panel.
Taiwan Patent Publication Number 200712713 (Publication Date: Apr. 1, 2007) reveals, in order to obtain a higher aperture ratio, an active device array substrate in which common electrodes serve as storage capacitors (Cs) is arranged below signal lines so as to increase the aperture ratio of the pixels. Referring to FIG. 1, a top view schematically illustrates a high-aperture-ratio pixel design in the conventional art, thereby explaining the pixel structures 100 having common electrodes which are disposed below the signal lines. The pixel structure has a plurality of signal lines 102 and a plurality of scan lines 104 which are perpendicular to the signal lines 102. A thin film transistor, (TFT) 110 is electrically coupled to each signal line 102 and each scan line 104 to serve as a switch. A drain terminal 116 of the TFT 110 is electrically coupled to a transparent pixel electrode 106 through a contact hole 117. A storage capacitor electrode 120 is disposed below the signal lines 102 and the drain terminals 116 to increase the aperture ratio of the pixel structures 100. In addition, there is an isolation layer (not shown) which is disposed between the storage capacitor electrode 120 and the signal lines 102 as well as the drain terminals 116.
This design increases the aperture ratio, however, if there are some defects formed in the production process, a short-circuit or an open-circuit may occur in the storage capacitor electrode 120 and the signal lines 102 and results in an image defect. Referring to FIG. 2, FIG. 2 is a schematic drawing illustrating a repair on the pixel structure of the prior art. Conventionally, when a short-circuit (as shown by a circle in FIG. 2) occurs between the storage capacitor electrode 120 and one of the signal line 102, the storage capacitor electrode 120 shared by the two adjacent pixel structures 100 should be disconnected by a laser cutting (as shown by dashed lines) to solve this problem. However, the repair via the laser cutting herein may cause the pixel electrodes 106 to be shorted with the storage capacitor electrode 120, resulting in a risk that the two adjacent pixel structure 100 become bad spots.
In addition, when an open-circuit occurs between the storage capacitor electrode 120 and the signal line 102 (as shown by an X in FIG. 2), the storage capacitor electrodes 120 shared by the two adjacent pixel structures 100 should be disconnected by a laser cutting (as shown by dashed lines), and the storage capacitor electrode 120 and the signal line 102 are welded as a short-circuit (as shown by ellipses in FIG. 2). However, there is also a risk of the pixel electrodes 106 to be shorted with the storage capacitor electrode 120.
Thus, the pixel structures whereby the common electrodes are arranged below the signal lines can not utilizing the laser cutting to repair the storage capacitor electrode. Accordingly, the display panel can only be scrapped, resulting in a waste in production cost.